/*
 * Copyright 2002-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.web.servlet.mvc.condition;

import java.util.Collection;
import java.util.Iterator;

import org.springframework.lang.Nullable;

/**
 * A base class for {@link RequestCondition} types providing implementations of
 * {@link #equals(Object)}, {@link #hashCode()}, and {@link #toString()}.
 *
 * @author Rossen Stoyanchev
 * @since 3.1
 */
public abstract class AbstractRequestCondition<T extends AbstractRequestCondition<T>> implements RequestCondition<T> {

    /**
     * Indicates whether this condition is empty, i.e. whether or not it
     * contains any discrete items.
     *
     * @return {@code true} if empty; {@code false} otherwise
     */
    public boolean isEmpty() {
        return getContent().isEmpty();
    }

    /**
     * Return the discrete items a request condition is composed of.
     * <p>For example URL patterns, HTTP request methods, param expressions, etc.
     *
     * @return a collection of objects, never {@code null}
     */
    protected abstract Collection<?> getContent();

    /**
     * The notation to use when printing discrete items of content.
     * <p>For example {@code " || "} for URL patterns or {@code " && "}
     * for param expressions.
     */
    protected abstract String getToStringInfix();


    @Override
    public boolean equals(@Nullable Object obj) {
        if (this == obj) {
            return true;
        }
        if (obj != null && getClass() == obj.getClass()) {
            AbstractRequestCondition<?> other = (AbstractRequestCondition<?>) obj;
            return getContent().equals(other.getContent());
        }
        return false;
    }

    @Override
    public int hashCode() {
        return getContent().hashCode();
    }

    @Override
    public String toString() {
        StringBuilder builder = new StringBuilder("[");
        for (Iterator<?> iterator = getContent().iterator(); iterator.hasNext(); ) {
            Object expression = iterator.next();
            builder.append(expression.toString());
            if (iterator.hasNext()) {
                builder.append(getToStringInfix());
            }
        }
        builder.append("]");
        return builder.toString();
    }

}
